Centrifugal fan casing



May 2l, 1940. K.D. MCMAHAN CENTRIFUGAL FAN CASING Filed June 24, 1958 w m O m H Inventor z mw 8 M MJ. D@ *WW e# K@ Patented May 21, 1940 PATENT OFFICE 2,201,867 CENTRIFUGAL FAN CASING Kenton D. McMahan, Schenectady, N. Y., assignor to General Electric Company, a corporation of New York Application June 24, 1938, Serial No. 215,643

1 Claim.

The presentl invention relates to centrifugal fan casings of the type having a plurality of outlets, and to portable electric tools equipped with such casings for motor Ventilating and cooling purposes.

The object of my invention is to provide an improved construction and arrangement in fan casings of this type and in portable electric tools equipped with such casings, and for a consideration of What I believe to be novel and my invention, attention is directed to the accompanying description and the lclaim appended thereto.

In the accompanying drawing, Figure 1 is a side elevation of a portable electric motor driven tool having fan casing embodying my invention; liig. 2 is a sectional view taken on line 2-2 of Fig. 1, and Fig. 3 is a sectional view taken on line 3-3 of Fig. 2.

Referring to the drawing, there is shown a portable electric motor driven tool comprising an electric motor I having a handle 2 at one end and a driving head 3 at the other end. The driving head is equipped with a suitable chuck I for holding drills and the like. The driving connection between the motor and the chuck is carried within the head 3.

Between the driving head 3 and the electric motor is a bladed centrifugal fan 5 keyed to the motor shaft 6. The fan has an inlet 1 at the center. Upon rotation, air is drawn into the motor casing through inlet openings 8 and through the motor casing to the fan inlet 1. The air is discharged from the fan to a casing which has end walls comprising the end wall 9 of the driving head 3 and the end frame I0 of the motor and which has peripheral wallsy comprising an. intermediate member II which is clamped therebetween. As shown in Fig. 2, the member II is of substantially square section. -It has an inwardly extending flange I2 provided with a circular opening I3 which fits over and is seated on a circular'boss Il on the wall 9 of the driving head 3 so that the flange I2 is substantially flush with the wall 3. Integral with and extending along ther edges of a fiange are walls I5 which project axially therefrom over the fan and bridge the space between the driving head 3 and the motor to provide the outer periphery of the fan casing.; The inner ends of the walls I5 terminate in cutoffs I6. The front faces I1 of the Walls I5 extend from the cutoifs to the outside of the casing and serve to direct air from the fan to discharge outlets I8 arranged in the corners of the fan casing. The inner surfaces I9 of the 5 walls I5 extend spirally beyond the cutoff in the f direction of rotation of the fan and overlap the faces I1 of the succeeding walls I5 to define the other sides of the discharge outlets. The inner surfaces I9 diverge from the periphery of the 10 fan and provide passages increasing in area. from the cutoff around the fan toward the outlets.

From one aspect, it is seen that the discharge passages for the fan are provided by spirally arranged walls having their inner ends terminat-J 15 ing in cutois I6 and extending therefrom along the sides of the fan casing in the direction of rotation of the fan and having the other ends overlapping the succeeding walls to provide the discharge outlets. The front faces I1 of the 20 walls are also spirally arranged, providing a gradual increase in area of the discharge passages and a gradual change in direction of the discharge of air. Due to the shape of the discharge passages it is substantially impossible to damage 25 in front of the cutois as regards the direction of rotation of the fanA and terminating at the outer surface of the casing for directing air to the ad- 40 jacent outlets, and walls extending from the cutois beyond the cutoffs as regards the direction of rotation of the fan and diverging from said first walls and terminating at the outer surface of the casing providing passages increasing in area in the direction of rotation toward the succeeding outlets.

KENTON D. McMAHAN. 

